1. Field of Invention
This invention relates to a power supply system, specifically to a power supply system including an AC source from a power grid and DC sources from local and remote alternative power sources.
2. Description of Prior Art
In recent years, concerns have been raised that high demand for electricity taxing the capacity of existing electricity generating plants. Furthermore, concerns regarding the availability and environmental safety of fossil and nuclear fuel are being raised. As a result of the above factors, the price of electricity has been on a path of steady increasing.
Furthermore, the electrical utility industry has for some time labored under the problem of supplying cost effective power to comply system peak-demand period requirements. The concept of peak-demand power supplementation is not new. A number of systems have been tested and implemented over years based upon batteries, hydroelectric, and combustion turbine. Each of the systems, by nature or by implementation, has had problems. Some are expensive and others are not acceptable environmentally.
Solar systems have been used with gained popularity to resolve at least partially the peak-demand issue of the power grid. A solar system may convert generated DC electricity from solar panels into AC electricity and be used to power electrical appliance. The generated DC power may be purchased by a power grid company after it is converted into AC power by utilizing an inverter. Over the years inverters have progressed from electromechanical to semiconductor devices. The use of the inverters not only causes the loss of electrical power but also the increase of overall cost of the solar system.
In addition to the solar systems, wind turbines have also been employed to provide clean energy. The wind turbine generates an AC power from the kinetic energy of the wind through a system comprises a rotator, a gearbox and a generator. The AC power is rectified into a DC power and is further converted into AC power with the same frequency as the AC power from the power grid. The inverter is used to convert the DC power into the AC power, which results in a loss of electricity and also in an increase in the cost.
It is desirable to have a system and method for utilizing the solar energy and/or wind turbines to supplement the AC power from the power grid while eliminating the use of the inverters to reduce the cost of employing the alternative power sources.